Vehicle brake pulsator and method of braking



Jan. 20, 1942. c. J. JAHANT ET AL VEHICLE BRAKE PLSATOR A ND METHOD OF BRAKING Filea sept. 1*'7, 1957 3 Sheets-Sheet 1 f .tyt. @MTW Mfh Jan j. mi @www www @wn Y mv ATTO R N EYS Jan. 20, 1942.

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c. J. JAHANr 'Er'AL VEHICLE BRAKE PULSATOE AND METHOD OF BRAKING Filed Sept 17, 1937 l 5 Sheets-Sheet 2 I'Nvlsmons- Charles J Jahant WiLLia/m 0.51960 Herman T. Kraft v ATTORNEYS Jan. 20, 1942. c. J. .JAHANT r-:TAL

VEHICLE BRAKE PULSATOR AND METHOD OF BRAKING Filed Sept. 17, 1957 l 3 Sheets-Sheet y Herma/n @l Kraft "l 'i 65 ai i Fi' lNvENToRs' @kurzes fa Jahn/nt William il., MC@ 0?@ BY lll lowered position; A

Fig. 5 is an elevational view partly in section Patented Jan.,20, 1942 VEHICLE BBAKEIULSATUB AND METHOD I F BRAKING Charles J. Jahant, Akron, William C. McCoy,

Shaker Heights, and Herman T. Kraft, Akron,

e. Ohio, assignorsto The General Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application September 17,1937, Serial No. 164,290

ziclaims.

This invention relates to brakes and more particularly to a pulsating brake that provides rapidly rrecurrent brake-diminishing and brake-increasing forces to brake-lockingtendencies and obtain more eilcient brake applications. 2

In the past it has been common practice, particularly among professional operators of-motor vehicles, to apply the brakes of their vehicles by the recurrent application of presslne to the foot pedal when on slippery roads and the like, as a meansof minimizing the'locking of the brakes in their applied position with the resultant decrease in the maximum emciency of the brakes in arresting the momentum of the vehicle and to minimize the tendency to skid.

For quick stops and in emergencies, the release of the brakes cannot be accomplished quickly enough by foot pressure to obtain kmaximum stopping efficiency from the brakes and it is only by the greatest presence of mind that even experienced operators are able to release and reapply their brakes unde'r emergency conditions be apparent to thoseA familiar with the art' to which the present `invention pertains, illustrative embodiments ofthe invention are disclosed in the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a "vehicle hydraulic brake system including a pulsation eiecting mechanism that embodies the present invention;

Fig. 2 is an elevational section of the b r-ake pulsation unit shown in Fig. 1 and enlarged withv respect thereto; i

Fig. 3 is an elevational section with parts removed of the brake pulsatingunit shown in Figs. 1 and 2; taken substantially on the line 3-3 of Fig. 1;.

Fig. 4 is a fragmentary elevational section similar to Fig. 2 showing the pulsating piston in the multi- 55 ple piston pulsating unit taken substantially the1ine66ofFig.5; A

Fig. 'Z is a diagrammatic representation of the fluid connections for a brake system employing 5Y amultiple piston pulsating unit; f

Fig. 8 is a diagrammatic vertical sectional view of a modified form of pulsating unit; Fig. 9 is a fragmentary vertical sectional view showing a modied form 'of pulsating unit actu- 10 ated from the cam shaft of an internal combustion engine;

Fig. 10 is a sectional view taken substantially on the line Ill-I0 of Fig.9;

Fig. 11 is' a fragmentary sectional view with parts broken away showing the latch releasing mezhfnism of the device illustrated in Figs. 5

Fig. 12 is an elevational view, partly in section and with parts removed, showing a modication of the invention employing four pulsating vchambers and pistons and corresponding to Fig. 5;

Fig. 13 is a fragmentary detail showing the relative positions of the actuating cams on the control shaft of the. embodiment shown in Fig. 12: and

Fig. 14 is a diagrammatic representation of the luidfconnections for a vbrake 'system employing the multiple piston pulsating unit illustrated inFig. 12. The present invention contemplaes a brakeactuating mechanism in which a pulsating unit is interposed between the braking means of the vehicle-and the lever or pedalactuated by the driver or operator or subject to his control. Suclr an arrangement may be applied to brakeswof any conventional character and in describing suitable embodiments of the invention the details of brake construction have been omitted, since they may be any of-a number of designs well known in `the art. i

The pulsating unit contemplated is` designed to cut off or interrupt the braking force applied by the driver of the vehiclevfor a series or succession of rapidly recurrent intermittent relatively-short time intervals. During the intervals that th'e brake-actuating force applied'by the vehicle operator is cut off the brake-applying force prior to cut-ofi is gradually diminished and then increased to substantially re-establish the original value prior'to cut-oi. Accordingly, ii the initial brake-applying force is sullcient .to lock'the wheels and cause skiddingthereof, the subsequent diminution of the brake-applying force releases the objectionable sln'dding which would otherthe wheels so that they may rotate and prevent wise interfere with the safe and effective braking of the vehicle.

After each interval of cut-oil the pulsator permits the actual braking force applied by the operator of the vehio1 to be momentarily transmitted,

to the brakes.

formed circumferentially about the. piston 22in` The embodiments of the invention illustrated I in the drawings are for use in connection with hydraulic braking systems. 'I'he arrangement of the pulsator is such that after an initial brake application the ilow of fluid through the iluid conduit from the pressure cylinder to the individual brakes is automatically arrested. andl by means of a suitably actuated liquid pump the brake fluid pressure in the lines communicating with the various brakes is diminished-and'then pulsations. After completion of, each pulsating cycle the high pressure -of the fluid conduit is put into communication with the several con- 1 increased in a.rapidly recurrent succession of duits leading to the various brakes to permit substantial equalization of the uid in the sevferal courses. Upon release of the brake-applyingl pressure the intensity of -the pulsations diminishes until the brakes are entirely released and`v the pulsator becomes inactive.

The embodiment of the invention illustrated in Figs. 1 through 4 showshousing I of the pulsating device secured to transmission 2 of an automotive vehicle. The pulsating device is connected by iiuid conduit 3 to the actuating cylinder or pressure developing chamber 4 of a oonventional hydraulic brake system in which foot pedal 5 is arranged through suitable linkage to compress the brake iluid in the actuating cylinder 4 b y means of a piston 8. A reservoir 1 is arranged above the cylinder 4 and communicates therewith through`a port 8 which is uncoveredA journalled in roller bearing assemblies I5 and I1.

This shaft has keyed thereto a gear I8 which meshes with a gear I9 of the vehicle transmission. Preferably the gear I9 is one of the gears connected to the driveshaft andwheels of the automotive vehicle so .that itis rotated by the movement of the vehicle. An eccentric 28 is secured or formed on the shaft |5 for rotation in a plane passing longitudinally through a.

cylinder 2| formed in' the housing I. The pulsating piston 22 is slidably received in the cylinder 2| and has a workingface 23 that engages the eccentric 28, as will be later described.

The end of the piston 22 opposite the working face 23, is axially bored to provide a cylinder which receives a ram 24. larged diameter base 25 which seats against the closed end of the cylinder 2| A helical compression spring 28 is disposed about the ram 24 and seats against the base 25 of the ram and the end of the piston 22 to normally urge the latter into engagement with the eccentric 28. 'A pulsating chamber 28 is thus dened internally of the piston 22 by the bo'. i and the ram 24. Normally the spring 28 tends to withdraw the ram 24 from pressed, fiuid pressure developed'in the actuating e cylinder 4 by the piston 8 is transmitted through Vthe conduit 3 and the fluid ilows through the inlet passageway 38 around the annular groove 29 in the piston 22 through the outlet passageway 3| to main line conduit I8, which distributes the high pressure iluidto the various branch line conduits II and the individual wheel brak cylinders I2 to actuate the brakes.

The pulsating chamber 28 communicates with the annular groove 29 adjacent the outlet passageway 3| through a passage 32. This passage terminates within the chamber 28 beyond the end of the ram .24 so as not to be obstructed thereby. A longitudinally extending groove 33 .is providedon the piston 22 and is continuous with the arnular groove 29 and passage 32. It also remains in communication with the outlet passageway 3| throughout the reciprocatory movement of the piston 22 so as to provide a continuous through passageway between the pulsattain the latter in raised position to provide a the bore to increase the volume of the pulsating continuous passageway from the iluid conduit 3 to the main line conduit I8 as described above. Actuating rod 31 of the latch 34 extends into an enlarged diameter cylinder 38 and is secured to a piston 39 slidable in the cylinder 38, The direction of movement of the latch 34 and its related parts is substantially normal to the movement of the pulsating piston 22 and the latch is nor? mally urged into engagement with the shoulder 35 of the piston by a helical compression spring 48. One end of this spring-seats against the piston 39 and the opposite end is received in a cup formed in cylinder closing cap 4|, the latter also serving to limit the withdrawing movement of thelatch 34 from the shoulder 35 by engagement of collar 42 of the cap with the piston 33. A vent 43 extends from a portion of the cylinde'r 38 adjacent the plugs 4| into the chamber for the shaft I5 to prevent Ventrapment ot air between the piston 39 and cap 4|.

In its retracted position illustrated lin Fig. 4, the latch 34 is not entirely withdrawn from the cylinder 2| and slides in a groove `44 extending ,longitudinally in the outer surface of the piston In this manner rotation of the piston 22 in the cylinder 2| is prevented and the groove 33 is maintained in communication with the out# --let passageway 3|.

'I'he ram 24 has an axial bore 48 which communicates with the pulsating chamber 28 and slidably receives .small piston 41 retained by a pin 48. A relatively strong compression spring 49 is received in the. bore 4 6 between. the piston 41 and. the base 25 to normally urge the piston 41 toward the vpin 48 and serve as a shock absorber and=safety device for the pulsator. v Preferably a vent 58 is yformed through the base of the ram and the housing also, a locating pin 5| has a press t in the housing I and base 25,

of the ram to prevent rotation or movement of the latter in the cylinder 2|.

A iluid passage 52 is formed in the housing and extends between the inlet passageway 3 I and latch chamber 38. When the foot pedal 5 is depressed andahigh iiuid prsure created in the cylinder 4 the iiuid is forcedthrough the conduit 3, passageway 30, annular groove 29, outlet passageway 3|, and the conduits I0 and II to the brake shoe cylinders I2 which apply the brake shoes I4. vto the brake drums in the usual manner. Simultaneously, the high pressure iiuid is forced through the passage 52 into the latch cylinder 38, to withdraw the latch 34 from the shoulder and release the pulsating piston 22 which moved into engagement with the eccentric 20 under the iniiuence of compression spring 26. The initial movement f the piston 22 seals the inlet passageway 38 to interrupt the ow of high pressure uid to the pulsator from the pressure- -ing force. The high pressure iluid in some instances may exert suflicient independent expandi ing force in the chamber 28 to move'the pistor. 22 without the spring 26.

The eccentric 20, rotating relatively rapidly under the influence of the engine or vehicle or some independent power source, engages the working face 23 of the piston 22 almost immediately after application of the brakes by the pedal 5. After initial contact between the eccentric 20 and the piston 22 the latter substantially rides on the eccentric so long as the braking force is appliedby the pedal 5. At each upward movement of the piston 22 under the inuence, of the eccentric 20 thepulsating chamber 28 is decreased in volume because of the movement thereinto ofthe ram v24|. Thisaction forces `the uid out the passage 32 and into the main line conduit I0 through the ylongitudinal groove 33 and outlet passageway 3|. Thus, at each raising of the piston 22 by the eccentric 20 there isa reapplication of the brakes to sub- Vstantially the degree initially applied by the foot pedal 5 prior to the cutting off of the high pres,- sure supply of iluid.v As soon as the pulsating piston is raised to its initial position the annular groove 29 uncovers the inlet passageway 30 so that an additional charge of high pressure iluid is allowed to pass from the high pressure, fluid conduit 3 through the'pulsating unit and into the main line conduit ||l and then to the brake cylinders I2 for reapplication of the brakes to a greater degree than before.

Thus, so long as the foot pedal remains idelparts have been identifiedv by the same nurner-L als of reference. Somey o!V the parts which are the same as in` the previous descriptionA havebeen given new numbers because of duplication and for clearness The housing I-is formed with two cylinders 54 and 55 which correspond to the cylinder 2| previously described. The pulsatingv pistons 22 in each Vof these cylinders operates in the same manner as that previously demribed.

They are reciprocated by eccentrics 56 and 51 secured on the shaft I5 `driven by any suitable means such for example as from the transmission as previously described or by the motor or engine of the vehicle or an auxiliary source. The eccentric 56 is out of phase with respect to eccentric 51 so that thecompression of the brake uid in the pulsating chamber of the piston in the cylinder 54 does not occur at the same time as the compression of the iiuid in the pulsating chamber of the piston in cylinder 55.. As shown v` in Fig. 6, the eccntrics are about 186 out of 34 are disposed in spaced parallel relationand fill pressed there is a series of rapidly recurrent Y brakeapplications and brake releases. The intensity of the brake application is at no time greater than that produced by the foot pedal 5,

and between each application the intensity decreases so that if the original application tended to lock-'the brakes and cause skidding of the.

similar to that previously described, and like 60 .to normally urge the latches to` the right, as

viewed in Fig. 6 into engagement with the pistons 22.

Retraction of the latches 34 is accomplished by yoke levers 64 which straddle the rods 31 and engage the collars 62 opposite the springs 63. The yoke levers are secured on shaft 65 journalled in'the housing I. -Both latch levers `may be.made integral, as shown, to insure simultaneous release of both pulsatingl pistons. Extending upwardly between the yoke levers 64 and desirably formed integral therewith isa lever 66, also pivotingV on the shaft 65. The end.of this lever has a socket which receives the end of rod 61 of latch piston 68 which is slidable in cylinder =69 formed in the housing I, the cylinder com 'municating with; the inlet passage 30" through short passage 1i). The piston 68 functions in a manner'similar to the piston 39 described in phase one of the pulsating pistons. will be rising while the other is falling, and vice versa.

Fig. '1 is a diagrammatic representation -oi" a ing pistons in the several cylinders is by means mainline ilbandbranchlinesllaandllb. V'I'he 5 rear brakes |2c and I2d for the right and left reail wheels respectively receive their rapidly recurrent energizations from the pulsating mechanism associated with cylinder 58 through the main line ila and branch lines llc-and yI Id respective- 10l ly. Thus, while the braking forceon the front wheels |2a and I2b is being increased by the com.-

pression of the brake fluid in the pulsating chamber 28 associated with the cylinder 68, the braking force-appued to' the rear wheels ne and ud is 15 being diminished by an increase in volume of lthe pulsating chamber 28 associated with the cylinder 55. In this manner a smooth braking action is 'appliedto the vehicle so that the occupants do not experience a jerking or rirregular movement. If desired, it is contemplated to use additional pulsating pistons to provide a pulsating chamber individually for each wheel which may be actuated out of phase with one another similar to the construction set forth in Figs. 5 and 6. The multiple cylinder form of the device is preferred for most installations since it provides a difference in timing of pulsations for the various wheels. If so desired, the pulsation period for the right front and left rear wheels may be the 3 the fluid same and different from the pulsation period for the left front and right rear wheels. A suitable multiple cylinder pulsator is `illustrated in Fig. 12. This modification ofthe invention is similar to the embodiment shown in Figs. 5 and 6 except u that four pulsating chambers or cylinders are employed in lieu of the two cylinders 58 and 55 previously described. In the fourfchamber device cylinders |8|| and |8| are formed in side by side parallel relation to one another in an upstanding portion |82 of the housing or casing l, and cylinders |83 and |88 are similarly formed in an upstanding portion |85 of the casing. The high pressure fluid from the pressure developing chamber 8 is supplied to the cylinders or chambers |88, |8|, |83 and |84 similarly to the manner in which such iiuid is supplied to the cylinders 58 and 55 previously described. 'I'he fluidchannels and grooves formed in the pulsating pistons 22 that reciprocate in the cylinders of the device shown in' Fig. 12 are connected by passages corresponding to the passages 3|, previously described, to individual'conduits |06, |81,

|88 and |68 that lead t0 the several brakes |2a, 55

|2b, |2c and |2d previously mentioned. In this manner a separate pulsating cylinder with its associated piston is provided for each of the four brakes of the vehicle. Actuation of the pulsatof a plurality of cams HI, H2, |I3 and III, se cured on the shaft I5 in different rotative positions and which correspond to the cams 56 and" 51 previously described. The cams for the several pulsating pistons may be arranged approxi- 5 mately 90 apart, as indicated in Fig. 13, so that the several pulsating pistons of the device shown in. Fig. 12 are operated sequentially and out of phase'with one another. `Such an arrangement promotes a smoother braking action and avoids 70 passing longitudinally through a cylinder 16' formed in the -cylinder block 12. A pulsating piston 11 has sliding engagement in the cyl- Linder 16 andhas a downwardly directed spacing boss 18 which engages head 18 at the closed end of the cylinder 16 to provide a fluid chamber 88 of small volume when the piston 11 is at its lower limit of movement. The high pressure fluid conduit -3 from the pedal actuated pressure chamber or cylinder is connected by fitting 82 to the cylinder block 12 and communicates with an inlet passageway l83 which terminates at a mid portion of the cylinder 16. In a similar manner the main line conduit I8 is secured to the cylinder block by a fitting 84 Awhich communicates with an outlet passageway ,85 tergominating in the cylinder 16 opposite the-inlet passageway 83. .An annular groove 86 is formed circumferentially about the piston 11 so thatwhen the latter is at its lower limit of movement -as viewed in Fig. 8 the groove registers g5 with both'the inlet passageway 83 and outlet vpassageway 85 to provide a continuous course for the brake uid through the cylinder block 12.

A bleeder passage 81 extends longitudinally of the cylinder 16 from the outlet passageway. 85 to chamber 80 in the closed 'end of the cylinder. Upon pressure being applied to Vthe foot pedal of .an automotive vehicle brake system forcing high pressure fluid through the conduit 3 the fluid flows through the inlet passageway 83 around the annular groove 86 of the piston 11 into the outlet passageway 85 and thence through themain line conduit I8 to the brake system. Simultaneously a portion of the high pressure fluid is bypassed from the outlet passageway 85 through the bleeder passageway 81 into the fluid chamber 88. 'Ihis uid raises the piston 11 so that the groove 86 moves beyond the port opening of the inlet passageway 83 into the cylinder 16, thus cutting oifthe flow of high pressure fluid to the brakes. High pressure iiuid continues to flow through the bleeder passage 81 into the chamber 88. from the main line conduit I8. This continues until working face 88 of the piston 11 is brought into contact with the eccentric 15 continuously rotated by the shaft 1l. The eccentric then forces the piston 11 downwardly into the cylinder 16, compressing the fluid in chamber 88 and forcing it through the bleeder passage 81 back into the main line conduit I8 and to the brake or brakes. As soon as the groove 86 uncovers the port of the inlet passageway 83 (provided fluid is still being suppliedunder pressure through the conduit 3) another charge of fluid is forced through the anco nular groove 86 into the main line conduit I0 to reapply the brakes with increased pressure, ya portion of this uid being bypassed .through the bleeder `passage 81 into the chamber 88 and again elevating the piston 11 to repeat the cycle. The working face 88 of ther piston follows the eccentric 15, being maintained thereagainst by the high` pressure iiuidin the chamber 80. The maximum braking pressure is applied when the annular groove 86 is in communication with the the braking pressure is then directly applied by the foot pedal. After th groove 86 moves past the port of the inlet passageway '83 the brak-j for example 75 ing pressure gradually diminishes on account of inlet passageway 83 and outlet passageway 85 sov that there is a through course for the iiuid and.

the fiow of the braking fluid into the chamber 80. This diminishing of the braking pressure continues until the piston 11 commences to move into the cylinder under the influence of the` eccentric 15. The braking pressure then increases, substantially to that prior to the closing of -the inlet passageway 83 -by the piston 11. Upon release of the foot pedal the pressure in the conduit 3 is relieved and when the piston' 11 is lowered by the eccentric l15, so that the inlet passageway 83 is in communication -with the annular groove 86, the high pressure fluid ows backwardl through the mainline conduit I of the braking system to the pedal-controlled actuz ating cylinder or pressure chamber.

thereto by studs 93. An extended body 94 is' formed integral with the cap member 92 and supported cantilever` fashion thereby internally of the engine. `This body portion is bored to provide a vertically extending cylinder 95 which corresponds to the cylinder 16 described in connection with Fig. 8. The location of the body 94 of the device is such that the cylinder 95 is disposed beneath an eccentric 96 carried by cam shaft 91 of the engine. The inlet passageway 83 and the outlet passageway 85 are arranged in parallel relation to one another, the former communicating with the cylinder 95 through an angularly disposed drill hole 98.

The operation of this modication is essentially like that of the device shown in Fig. 8. In both cases the pulsating piston 11 normally rests by gravity on the closed end 19 of the cylinder so that it is out of engagement with its actuating subject of the present invention. Essentially, the' present brake system uses, to create a primary pressure in the brake iiuid, a means actuated by the vehicle operator, and therefore termed a ./manual means, whether actually operated by foot or hand, in distinction to mechanically oper- 1. The method of retarding the velocity of ay vehicle having pedal-actuated friction :brakes which comprises applying a primary load to the brakes through the pedal, automatically rendering the pedal ineffective to energize the brakes for a series vof rapidly recurrent, relatively shorttime intervals, alternating with time-intervals during whichl the braking force is determined by the pedal pressure and a succession of primary loads is established, and automatically varying the braking load during the time intervals that the pedal is ineiective to produce a succession of l the. pedal is ineective to produce a succession of.

secondary loads.

2. The method of retarding the velocity of a vehicle having pedal-actuated friction brakes which comprises applying a primary load to the brakes through the pedal, automatically rendering the pedal ineffective to energize the brakes for a series of rapidly recurrent, relatively shorttime intervals,l alternating with time intervals during which the braking force is determined by the pedal pressure and a succession-of primary loads is established, and automatically varying the braking load during thetime intervals that secondary loads, each secondary load being of .less amount' thanthe preceding primary load.r

3. The method of operating hydraulic vehiclel brakes having a pressure-developing cylinder arranged to be energized by the vehicle operator and brake-actuatingcylinders connected to the ated means such as the pulsating piston 22..-

in both the method and apparatus, may be em' ployed, change being made as regards the details described, -it being understood that the particular forms shown and described and the proced e set forth are presented for purposes of exp tion and illustration. g

pressure-developing cylinder by a hydraulic system which comprises creating a iiuid pressure in Athe pressure-developing.cylinder to apply the brakes under a primary load. automatically closing the hydraulic connection between the actuating cylinders and pressure-developing cylinder, and automatically creating a series of rapid pressure pulsations in the portion of the hydraulic system between the. closure region and the` actuating cylinders.

4. The method of operating hydraulic vehicle brakes having a pressure-developing cylinder arranged to be energized,V by the vehicle operator and brake-actuating cylinders connected to the pressure-developing cylinder by a hydraulic system which comprises creating a fluid pressure in the pressure-developing cylinder to apply the brakes under a primary load, automatically closing the hydraulic connection between the actuating cylinders and pressure-developing cylinder, automatically lowering the iiuid pressure in the portion ofthe system remaining in iiuid communication with the actuating cyilnders to reduce the primary load by a predetermined amount and establish a secondary load, automatically raisingthe uid pressure in said portion of the system to increase the braking. load and substantially reestablish the 4primary load, and automatically opening the communication between the actuating cylinders and the pressure-developing cylinder to permit equalization of fluid pressures in the system and regulation of the primary braking load to accord with that produced in the pressure developing cylinder.

5. In a vehicle hydraulic brake mechanism having a conduit for carrying high pressure uid fromf a pressure chamber to energize the brakes the combination of a pulsator interposed in the conduit, said pulsator including a piston disposed in the path of fluid through, the pulsator and movable to substantially arrest the iiow of iiuid, and means for reciprocating the piston upon an increase in fluid pressure in the conduit.

6. In a vehicle hydraulic brake mechanism having a conduit for carrying highl pressure fluid from a pressure chamber to energize the brakes the combination of a pulsator interposed in the conduit, said pulsator including a chamber com- ,municating with the conduit, and automatic means ior alternately increasing and decreasing the sizeof the pulsator chamber to produce a series oi Apressure pulsations oi relatively small magnitude inthe conduit, said automatic means being arranged to substantially arrest the ilow of fluid into the pulsator chamber from the pressurefchamber in timed relation with th'e pulsations.

7. In a vehicle hydraulic brake mechanism having a conduit for carrying high pressure fluid vfrom a pressure chamber .to energize the brakes the combination of a pulsator interposed'in the conduit, said pulsator including a .chamber 'communicating with the conduit, movable means in the pulsator chamber for alternately increasing and decreasingthe volumewthereof to produce a series of pulsations of relatively small magnitude inthe conduit, and the movable means arranged to substantially arrest .the ilow of fluid into the pulsator chamber from 'the pressure chamber while ithe pulsator chamber is at its greatest vol-- ume. 8. In a brake system, means for manually applying a primary load to a brake, means movable upon the application of said load to arrest the .l manual application and automatically reduce the load previously applied manually, and then automatically increase the reduced load, and means for actuating the movable means.

, brake iluid, manually operated means for comtuatingfthe latter to produce said pressure alternations. and means for holding the recipro' cable means out oi'- engagement with the actuating means and in `said normal position, said holding means. being responsive to the manual means yto release the reciprocable means for reciprocation thereof by the actuating means upon the application of a primary pressure to the 'Abralr'e iluid by the manual means, and to perpressingthe nuid, a housing,4 a chamber in the housing for receiving compressed iluid from said manually operated means, a passageway in Ithe housing through which iluid from the compressing means ilows to the chamber, means in the chamber for alternately decreasing and increasing the pressure on the uid, said last named means arranged to substantially arrest the iiow of uid .through said passageway during said decreasing and increasing of. the nuid pressure in the chamber, and means for actuating the pressure decreasing `and increasing means independently og the manual means.

A11. In a hydraulic brake system, a brake responsive to hydraulic pressure, manual means for applying a primary pressure load to a brake iiuid, a chamber to receive high pressure'iiuid from said manual means and deliver high pressure uid to the brake, reciprocable means for creating a rapidly recurrentseries oi' alternating pressure decreases and pressure increases in the chamber, said reciprocable means being arranged to permit the relatively free ilow of fluid from the manual means to the brake while in normal position, and while in another position, to substantially arrest `the flow of high pressure iluid from the manual means tothe brake, means -en'gageable with the reciprocable means for ac-y brake, a conduit for uid connecting the fluid supply means to the brake, means including a mit the reciprocablemeans to move to said second named position.

12. Apparatus for retarding the velocity of a moving body, comprising a brake responsive .to iluid pressure, a pulsating chamber for iluid having substantially continuous `iluid connection with the brake, a manually controlled source of iluid under pressure, means eiecting iiuid connection between the sourceand chamber, means for interrupting said klast named connection during 'a series oi rapidly recurrent intermittent Y time intervals, and means for decreasing and increasing the chamber volume during said time intervals to subject .the brake to a series of rapidly recurrent pressure increases and decreases.

13. Apparatus for retarding the velocity ot a moving body, comprising a plurality of bralresA responsive to fluid pressure, a pulsating chamber for iiuid having substantially continuous uid connection with one of the brakes, another pulsating chamber having substantially continuous fluid connection with another brake, a manually controlled source of uid under pressure, means eiecting=uid connection between the source and each ofthe chambers, means for interrupting the connection between the source and the first named chamber during a series of rapidly recurrent -intermittnt time intervals, means for interrupting .the connection between the source and the seconddnamed chamber during a second series of rapidly recurrent intermittent time intervals noncoincidenty with said first named series of time intervals, and means for decreasing and increasing the volume of each chamber during each of said time intervals of the series associated therewith to simultaneously subjectthe several brakes to noncoincident pressure pulsations.

14. In a brake system for a vehicle a iluld responsive brake, means operable bythe vehicle operator for 'supplying iiuid under pressure to the brake, a conduit for fluid connecting the fluid supply meansto the brake, means including a piston and pulsating chamber interposed in the conduit for controlling the fluid pressure apf plied to the brake, saidcontrolling means being formed to provide a relatively unobstructed passage fornuid moving through the conduit in one position of the piston and to provide a substantially fluid-tight closure for the conduit in another position of the piston, and means for reciprocating the piston between said positions to alternately open and close the fluid passage through the control means and thereby subject the brake to fluidpressure supplied 4by the operator during a series of discontinuous time intervals which alternate with time intervals during which the iluid connection between the supply means and the brake is disestabllshed.

' 15. In a brake system for a vehicle, a fluid responsive brake, means operable by the vehicle operator for supplying fluid under pressure to the pistonand pulsating chamber interpose4 in,the conduit for controlling the fluid pressuredhp pliedto the brake, said controlling means being formed to provide a relatively unobstructed passage for luid moving through the conduit in one position of the piston and to provide a substantially uidtight closure for the conduit in another position of the piston, means for holding the piston in said one position, means responsive to an increase in uid pressure in the conduit to actuate the holding means to release the piston, and means for reciprocating the piston between said positions to alternately open and close the. uid passage through the control means andthereby subject the brake to fluid pressure supplied by the operator during a series of discontinuous time intervals which alternate with time intervals during which the uid connection between the supply means and the .brake'is disestablished.

16. The method of controlling the retarding of a wheeled vehicle having brakes towhich variable pressure can be applied to actuate the same, which comprises interrupting applied pressure during a series of discontinuous time intervals, and lowering the applied pressure a substantially constant amount during each interval to establish a. discontinuous series of intermediate pressures each -of which is less than and proportioned to the preceding applied pressure.

17. The method of controlling the retarding of a wheeled vehicle having brakes to which :variable pressure can be applied to actuate the same,

moving body which comprises applying to the body a discontinuous series of frictional loads of diierent amounts, and duringthe intervals be- Y tween successive loads only decreasing the loads sufliciently to establish intermediate loads of different amounts which are proportional to theV preceding applied loads.v

19. The method of 'retarding the velocityof a vehicle having supporting wheels equipped with friction brakes, which comprises manually apply- Ving a load to the brakes and mechanically decreasing and increasing the load by relatively small amounts materially less than the manual load in rapidly recurrent alternations and in respnse to said manual load application, the energizing ofeach of said mechanical load increases being independent of the continued application of the manual load, and the mechanicalincreassystem which comprises applying pressure on-the brake uid to provide a primary braking force on the brake, linterrupting the hydraulic connection between the brake and the point of pressure application during each of a series of rapidly recurrent time intervals, and separately pulsating the pressure on the uid during the intervals.

21. The method of operating a hydraulic brake system which comprises applying pressure on theV brake iiuid to provide a primary braking Vforce on the brake, interrupting the hydraulic connection between the brake and the point of pressure application during each of a series of rapidly re` current time intervals, and mechanically lowering and then raising the pressure on the uid over` aV predetermined relatively small pressure range during the intervals to effect a pulsation of the pressure on the uid.

CHARLES J. JAHANT. WILLIAM c. 'Macon :HERMAN T. KRAFT. 

